To the barkeep today, Jerry Thomas is the progenitor of all things mixology. A 19th-century bartender of great showmanship and skill, Thomas made his own bitters and infusions, and is credited with developing recipes for the margarita and Tom Collins, publishing the first drink book in the U.S, and elevating alcohol from something swilled in saloons to an ingredient rife with possibility. At the height of his influence, in the early 1860s, Thomas was earning more per week than Hannibal Hamlin—the vice president of the United States, in case you forgot. “Get you drunk, get your lady drunk, set some shit on fire, I can do it all,” he is reputed to have said. And while Thomas’s influence on the landscape of drinks can be seen on any given night, in any given bar, the strongest dedication to him may be found behind a dark door down a nondescript alley in the heart of one of the world’s most enchanting cities: Rome.

But gaining access to this bar—the aptly named Jerry Thomas Project—isn’t so easy. In true speakeasy style, visitors are prompted to provide a password in order to gain entry into the space, which has been open near Chiesa Nuova since 2010. The password is the answer to a question, and these questions (found on the bar’s Web site) change frequently with no rhyme or reason. They are typically related to old drinks and characters in the history of mixology, tied to Thomas’s magnum opus, Bartender’s Guide: How to Mix Drinks, or skew toward the technical: What do you call the part of whiskey that evaporates from wooden barrels during maturation?

Courtesy of Martina Monopoli.

Inside the small, dimly lit space, which can host 30 to 40 guests at a time, patrons perch on leather couches and order drinks from bartenders, who shake, stir, and strain signatures comprising the bar’s own gin and vermouth. There aren’t many rules here, but there are some: pay in cash only, don’t use flash photography, and smoke in moderation. Never, ever ask for vodka.

Leonardo Leuci, one of the bar’s founders, says the impetus for the Jerry Thomas Project originated in casual conversation.

“The idea [came about] almost by accident,” says Leuci. “We were sipping a beer and discussing what was happening around the world concerning classic mixology and the trend of speakeasy bars spreading from London to New York. That’s when we thought it was time to give a shake to our city, which was still ‘asleep.’”

Five years later, the lights are still on, though very, very dim.

The Jerry Thomas Project is open Tuesday through Saturday, from 10 P.M. to 4 A.M. Drinks start at $10. Reservations required.